Until recently, the environmentally harmful CFC(R-12) type refrigerant fluid was commonly used in automotive air conditioning systems. In 1991, however, the automotive industry introduced new air conditioning systems which employ a relatively less harmful HFC-134a type refrigerant. The newer HFC systems include specifically designed access fittings.
These access fittings typically include a permanent fluid fitting located on the air conditioning system, as a charging/access port, and a quick disconnect coupling for removeable connection to the permanent fluid fitting. The permanent fluid fitting is formed as a Schroeder-type valve which permits recharging, purifying or recovering of the refrigerant in the system and also fluid pressure measurements to be made. The quick disconnect coupling is typically attached to a flexible hose and to a supply or evacuation cannister for the refrigerant. As an example, for recharging an automotive air conditioning system with refrigerant, a quick disconnect fluid coupling, attached to a supply cannister of refrigerant, is sealingly connected to the permanent fluid fitting of the system.
In general these access fitting (i.e. permanent fluid fitting/quick disconnect coupling) differ in size from the access fittings used in the older CFC systems. Because of this difference, CFC refrigerant can not be accidently introduced into a newer system containing the HFC type refrigerant. This prevents the cross-mixing of refrigerants and lubricants which may damage an air conditioning system.
Standards for the HFC access fittings have been defined by the Society of Automotive Engineers (SAE). Under these standards the access fittings must be adapted for quick coupling and uncoupling. In addition, the access fittings must be designed to prevent discharge of the refrigerant into the atmosphere during coupling and uncoupling.
In order to satisfy these criteria, many quick disconnect couplings, suitable for use with the newer air conditioning systems, were designed with a manually rotatable screw type valve, for controlling fluid flow through the coupling. With such a manual flow control valve, the quick disconnect coupling can be sealed prior to connection or disconnection from the fluid fitting for the system. An example of this type of coupling is disclosed in U.S. Pat. No. 5,139,049 to Jensen et al., which is assigned to Aeroquip Corporation.
A major disadvantage of quick disconnect couplings having such a manually actuated flow control valve, is that the valve handle is sometimes difficult to operate in tightly enclosed spaces. In automotive applications where space is limited, this is a serious disadvantage. Specifically, the user of the quick disconnect coupling will be inconvenienced by having to rotate the valve handle until the flow control valve of the coupling is desirably positioned. Additionally, such couplings do not automatically seal upon uncoupling. Should the user therefore, forget to close the flow control valve of the coupling during uncoupling, some refrigerant may escape into the atmosphere.
For convenient use even in tightly enclosed spaces, quick disconnect couplings having self-sealing valves have been developed. The self-sealing couplings generally employ an internal Schroeder type flow control valve mounted within the coupling. Normally, the flow control Schroeder valve is urged into a closed position by a spring. During connection with a fluid fitting of a refrigeration system, the valve stem of the Schroeder valve and the mating parts of the fluid fitting are placed into contact. This opens the Schroeder and permits fluid flow through the coupling. Upon uncoupling the spring closes the flow control Schroeder valve to prevent the flow of any fluid through the coupling. U.S. Pat. No. 5,080,132 to Manz et al. discloses such a self sealing quick disconnect coupling.
A problem associated with the above described self-sealing couplings is that the flow control valve incorporated into the coupling may open prematurely during connection with a fluid fitting allowing refrigerant to escape. This may happen when the valve pin of the flow control valve for the coupling is actuated by the mating parts of the fluid fitting before the fluid fitting is sealingly engaged with the coupling. Furthermore, the flow control valve may not close quickly enough to prevent the discharge of refrigerant into the atmosphere during uncoupling of the coupling. In addition, high pressure developed within the coupling may cause the coupling to be blown apart from the fluid fitting causing injury to the user and to the coupling.
In view of the shortcomings of the prior art, the present invention is directed to a self-sealing, quick-disconnect coupling which can be safely operated and with minimal fluid loss during coupling and uncoupling. Accordingly, it is an object of the present invention to provide a quick-disconnect coupling that is self-sealing to prevent fluid loss during coupling and uncoupling. It is a further object of the present invention to provide a quick-disconnect coupling having an integral flow control valve formed with an adjustable valve pin for improved sealing during coupling and uncoupling to a fluid fitting. It is yet another object of the present invention to provide a quick-disconnect coupling which is relatively small in size and safe and convenient to use, even in tightly enclosed spaces.